Flow characteristics of a wall-attaching oscillating jet over single-wall and double-wall geometries

Abstract

This paper presents the experimental results of two-dimensional time-resolved particle image velocimetry (2D-TR-PIV) measurements for two external geometries of a sweeping jet: a single-wall geometry and a double-wall geometry. The single-wall geometry has a non-confined backward-facing step, and the double-wall geometry has a confined step with a sudden expansion domain. The effect of the Reynolds number based on the hydraulic diameter (D) and mean velocity of throat (U) was also studied in the range of 2000–10,000. The results show that the frequency of the oscillating jet is almost independent of the shape of the external region and varies almost linearly with the Reynolds number. In contrast, the velocity distribution of the flow is controlled by the external domain. The time-averaged velocity and vorticity data were acquired for the highest Re in the double-wall geometry, and there were three main vortices in the external domain that control the velocity distribution and a clear difference is observed. Other fields of view were also investigated in three different sections and the reattachment locations measured at a distance of 0.05D from the wall. The time-averaged results show that for both geometries, reattachment length was observed to decrease to the increase on Reynolds number.